Telephonic communications – Substation or terminal circuitry – Amplifying
Patent
1986-02-18
1988-09-20
Lev, Robert
Telephonic communications
Substation or terminal circuitry
Amplifying
379 52, H01M 160
Patent
active
047730889
ABSTRACT:
An amplifier for controlling the volume in a telephone instrument of the general type including coin-operated and pay type telephone instruments is enclosed in the telephone housing and provides a number of discrete, predetermined amplification levels selectable by operating a push-button switch also located in the housing so that its plunger extends through an opening in the telephone instrument face. The amplification level is automatically restored to a volume associated with a normal hearing sensitivity at the start of a new call and a dial shunt circuit suppresses the DTMF tones heard by a user when tone dialing is used.
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Mims, Forrest M., III, "Engineer's Notebook II", .COPYRGT.1982 by Radio Shack, p. 120.
Lev Robert
Tek Electronics Manufacturing Corporation
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